Telephone-switchboard.



C. C. ALLER & O. BEKKEDAHL.

TELEPHONE SWITCHBOARD.

APPLICATION flLED NOV. 8. 1911.

Patented Nov. 26, 1918.

UNTTED STATE LSiPATENT @FFKQE CHESTER C. ALLER AND OLE BEKKEDAHL, 0F PORTAL, NORTH DAKOTA.

TELEPHONE-SWITCHBOABD.

Application filed November 8, 1917.

To all whom it may concern:

Be it known that we, CHESTER C. ALLER and OLE BEKKEDAHL, citizens of the United States, residing at Portal, in the county of Burke and State of North Dakota, have invented certain new and useful Improvements in Telephone-Switchboards, and do hereby declare the following to be a full clear, and exact description thereof, reference being had to the accompanying drawings, forming part of this specification.

Our invention relates to telephone exchange systems and seeks to provide a simple and effective circuit arrangement of the common battery switchboard type which is especially adapted for use in small city and town systems to take the place of the usual magneto system and which is capable of being installed and maintained at a low cost.

Another object of the invention is to reduce to a minimum the number of contacts in the talking circuit and the number of apparatus elements connected in or with the talking circuit.

A further object is to provide an automatic control .of the connection of the listening and ringing circuits with the line.

Other objects of the invention will be de scribed and illustrated in the following specification and claims and the accompanying drawing.

The drawing represents diagrammatically two subscribers sub-stations, line circuits, and an operators interconnecting circuit at the exchange.

Referring in detail to the drawing, A and B represent subscribers sub-stations equipped with the usual talking apparatus arranged to be connected across the associated line when the subscriber raises the receiver from the switch hook. The line ter minal circuit arrangement of the sub-stations being identical, a detailed description of one will suflice. The line conductors 1 and 2 of the sub-station A terminate at the central oflice in the tip and ring contacts 3 and L, respectively, of a jack 29 from which their connection is extended through normally closed contacts 5 and 6 to a line relay 7 and the central office battery 9. A normally open contact 10 on the relay 7 controls line lamp 11 the circuit of which may include the windings of the usual alarm relay such as 12. The sleeve contacts, such as 13, of all the jacks are connected to the Specification of Letters Patent.

Patented Nov. 26, 1918.

Serial No. 200,965.

grounded side of the exchange battery as indicated at 14.

Each cord circuit at the central station consists of an answering plug 15 and a calling plug 16,- the ring contacts 17 and 18 of which are connected by conductors 19, 20 and 21 through a condenser 22 while the tip contacts 23 and 24 are connected by conductors 25, 2-6 and 27 through a condenser 23. Current is supplied from a suitable source such as the common battery 9, the current supply to the answering side of the cord being through a double wound battery supply relay 30, while that to the calling side is from the free or ungrounded side of battery 9 through a battery supply relay 31 and conductor 32 to the upper or ring conductor 20 and from the grounded side of battery through the battery supply relay 33 and conductor 34 to the lower or tip conductor 26. Relay 30 is provided with a normally closed contact connecting one terminal of the answering supervisory lamp 35 through conductors 36 and 37 to the free side of battery. The other terminal of the lamp 35 is connected through conductor 38 to the sleeve contact 39 of the answering plug. The calling supervisory lamp 40 is similarly connected between the sleeve contact 41 of the calling plug 16 and the free side of battery through a normally closed contact on the battery supply relay 33. Relay 31 is provided with a locking contact l2 which upon closure connects the conductor 53 which is connected through a retardation coil 54 and conductor 55 to the sleeve contact of the calling plug 16. A second contact 56 on the relay '31 normally connects an interrupter 57 through conductors 58 and 59 to one terminal of a ringing relay 60 whose other terminal is connected through conductor 55 to the sleeve tl of the calling plug 16, the interrupter 57 being connected through conductor 37 to the free side of battery. The ringing relay 60 is provided with a pair of movable armature contacts 61 and 62 permanently connected with the cord conductors 21 and 27 and arranged to normally connect them with the conductors 20 and 26 through normally closed contacts 63 and 64 respectively, and upon energization to disengage the contacts 63 and 64; and engage the normally open contacts 65 and 66 to connect the ring and tip cord-conductors 21 and 27 to the ringing leads 67 and 68. These ringing leads connect with the terminals of a common ringing machine 69.

A listening relay 70 is associated with each cord and has one terminal connected through conductors 71 and 37 to the free side of the battery 9, and the other terminal connected through conductor 55 to the sleeve contact 11 of the calling plug. This relay controls the connection of the listening multiples 72 and 73 of an operators telephone set, not shown, With the conductors 19 and of the calling plug through normally closed contacts 7 4 and 75, the listening multiples 72 73 being connected with the o erators telephone set through condensers 67 7 From the above, it will be seen that there is only one pair of contacts in the cord talking circuit,the normally closed contacts of the ringing relay, and that there are no bridges across the talking circuit other than the necessary battery bridge through the battery supply relays which, of course, are wound to prevent the passage of the voice currents, according to the usual practice in the art. This simplification of the cord talking circuit is of obvious advantage in operation and maintenance.

On operation, the subscriber at sub-station A desiring a connection with the subscriber at sub-station B, raises his receiver from the switch-hook which closes his line circuit 1-'2 through his sub-station apparatus in the usual manner, whereupon current from battery 9 passes out and back over the line wires 12 of the sub-station A by way of the windings of the line relay 7 and the normally closed ack spring contacts 3l. This energizes the line relay 7 which attracting its armature closes the normally open contact 10, closing the circuit or the line lamp 11. This circuit may be traced from the free side of battery 9, through contact 10, lamp 1 1, winding of relay 12 and through ground back to battery 9. The operator, upon observing the lighted lamp, inserts the answering plug 15 into the jack 29 of the sub-station A, the tip and ring contacts 23 and 17 of the plug engaging the tip and ring jack springs 3 and 1, of the jack respectively, causing them to separate and disengage from the normally closed contacts included in the circuit of the line relay 7 which thereupon becomes deenergized and extinguishes the line lamp 11. Current is now supplied to the line 12 of the calling sub-station from the common battery 9 through the windings of battery supply relay 30, cord conductors I925, plug contacts 17'23 and jack contacts 4='3. This causes the battery supply relay 30-170 become energized and open its normally closed contact which opens the connection between the answering supervisorylamp and battery Wire 37, one terminal of the lamp remaining connected to ground through conductor 38,

plug contact 39 and jack conta'ct13. Also, at this point in the operation, the operators listening multiples 72-73 are connected across the ring and tip conductors 19 and 25 of the cord circuit through the normally sub-station B, the operator inserts the calling plug 16 in the jack 78 of that sub-station. The insertion of the plug 16 in the jack 7 8 opens the normally closed jack contacts and brings the tip, ring and sleeve contacts 24, 18 and 41, respectively, of the plug into engagement with their respective compleinentary contacts of the jack, connecting the cord conductors 21-27 with the line wires 81-82 of the sub-station B and connecting the sleeve terminal 41 of the plug with the grounded side of battery through the grounded sleeve terminal 79 of the jack. This completes the energizing circuits of the calling supervisory lamp t0, the listening relay 70, and the ringing relay 60. The circuit of lamp 4'0 may be traced from the free side'of battery 9, normally closed contact of relay 33, lamp 40, plug sleeve-l1, jack sleeve 79, to ground and back to battery. The circuit of the listening relay 70 may be traced from the free side 01 battery 9, wire 37, 71, relay 70, wire 55, plug sleeve 41 and back to the grounded side of battery as before traced. Energization of the relay 70 opens the contacts 7-l75 disconnecting the operators listening set from the cord conductors. The circuit of the ringing relay may be traced from the! free side of battery 9, through wire 37, interrupter 57, 58, contact 56, wire 59, relay 60, wire 55 and through plug sleeve 41 back to the grounded side of battery over the path previously described. As the interrupter makes and interrupts the circuit, the ringing relay is correspondingly energized and deenergized. Each time the ringing relay is energized,-it opens the con tacts 636st and closes the contacts 6566, disconnecting the cord conductors 2127 from their continuations 2026 and connect ing them with the ringing leads 6768, thus applying ringing current to the line of the called substation B. The subscriber at substation B, answering the call, removes his receiver from the switch-hook closing his line circuit which, upon the neXt succeeding clei rnergization of the ringing relay, permits battery current to flow out and back over the line 8182 from the battery 9 through battery supply relays 3l33, conductors 32 34-, 2026, contacts 63-64, and cord conductors 2127. 1

Relay 33, becoming energized, opens its normally closed con-tact extinguishing the calling supervisory lamp 40, while relay 31, becoming energized, closes its locking cirion llU

cuit through contact 42 and opens the energizing circuit of the ringing relay 60 at contact 56. The locking circuit of the battery supply relay 31 may be traced from the free side of battery 9, through wlndmgot relay 31, 52, 42, 53, including retardation coil 54, and thence through conductor and plug contact 41 to the grounded side or battery as previously traced. A talking circuit between the sub-stations is new completed through the cord connections which 1s free of any relay contacts except the normally closed contacts of the ringing relay.

At the end of the conversation, should the called party hang up his receiver first, opening his line circuit, the battery supply relay 31 will remain energized over its looking circuit until the calling plug 16 1s w 1thdrawn thus holding the circuit of the ringing relay open at contact 56 and prevent1ng ringing current from being pplled back on the called line. The supply relay will, however, become deenergized immed ately the line circuit 8281 is opened, permitting its normally closed contact to complete the circuit of the calling supervisory lamp 40 over the following path; battery 9, contact of relay 33, lamp 40, through plug contact 41 to ground and back to battery 9. llhcn the calling party at sub-station A replaces his receiver. opening the line circuit -9 the double-wound battery supply relay 30 becomes deenergized closing the circuit of the supervisory lamp 35. The operator perceiving either lamp signal Withdraws both cord plugs, restoring the circuits and apparatus to normal condition.

While a specific embodiment of the invention is herein illustrated and described, it is to be understood that the invention is not limited thereto but that all such modifications and variants thereof as fairly fall within the scope of the appended claims are contemplated, and that the terms plug and jack are to be construed as including their equivalents in other forms of manual apparatus or automatic switching apparatus.

hat we claim is:

1. In atelephone exchange system, subscribers lines and jacks therefor at the central o'lfice, an operators cord circuit having answering and calling plugs, cooperating with said jacks for interconnecting said subscribers lines, a ringing relay having contacts in the cord circuit and operable upon insertion of the calling plug in the jack of a called line to open the cord circuit between the answering and calling plugs and apply ringing current to the calling end of the cord conductors, said cord circuit having permanent connections between the contacts of the ringing relay and said plugs, and a self locking relay through the windings of which current is supplied to a substation through the calling end of the cord circuit operable upon closure of the called line circuit to disable said ringing relay and close its locking circuit through contacts in the calling plug and the jack of the called line.

In a telephone exchange system, subscribers lines and jacks therefor at the central oiiice, an operators cord circuit having answering and calling plugs cooperating with said jacks for interconnecting said subscribers lines, a ringing relay hzning contacts in the cord circuit and operable upon insertion of the calling plug in the jack oi a called line open the cord circuit 1wtween the answering and calling plugs and apply ringing current to the calling end of the cord conductors, a self-locking relay through the windings of which current is supplied to a substation through the calling end of the cord circuit operable upon closure of the called line to disable said ringing relay and close its locking circuit through contacts in the calling plug and the jack of the called line, and a retardation coil arranged to retard the passage of talking currents through said locking current 3. In a telephone exchange system, subscribers lines and jacks therefor at the central ofiice, an operators cord circuit having answering and calling plugs cooperating with said jacks for interconnecting said subscribers lines, a ringing relay having contacts in the cord circuit and operable upon insertion of the calling plug in the jack of a called line to open the cord circuit between the answering and calling plugs and apply ringing current to the calling end of the cord conductors, a self-locking relay through the windings of which current is supplied to a substation through the calling end of the cord circuit operable upon closure of the called line to disable said ringing relay and close its locking circuit through contacts in the calling plug and the jack of the called line, and a retardation coil included in series in the locking circuit of said battery supply relay, together with an operators listening circuit and a listening relay operable upon the ini sertion of the calling plug in the jack of a called subscribers line.

4. In a telephone exchange system having subscribers lines terminating in jacks at a central office, an operators cord circuit having answering and calling plugs cooperating with said jacks for interconnecting subscribers lines, a supervisory circuit associated with said cord circuit andarranged to be closed through a contact on the calling plug and any one of said jacks, a calling supervisory signal a listening relay and a ringing relay energized over said supervisory circuit, a self-locking battery supply relay for one side of the calling end of the &

cord circuit operable upon energization to disable said ringing relay and lock itself over said supervisory circuit, and a second battery supply relay for the other side of the calling end of the plug circuit operable upon energization to disable said supervisory signal.

5. In a telephoneexchange system having subscribers lines terminating in jacks at a central office, an operators cord circuit having answering and calling plugs cooperating with said jacks for interconnecting subscribers lines, a supervisory circuit associated with said cord circuit and arranged to be closed through a contact on the calling plug and any one of said jacks, a calling supervisory signal a listening relay and a ringing relay energized over said supervisory circuit, a self-locking battery supply relay for one side of the calling end of the cord circuit operable upon energization to disable said ringing relay and lock itself copies of this patent may be obtained for five cents each, by addressing" the Commissioner of Patents,

over said supervisory circuit, and a second battery supply relay for the other side of the calling end of the plug circuit operable upon cnergization to disable said supervisory signal, together with means in the locking circuit for preventing the passage of the voice currents thereover.

6. In telephone exchange system, a link circuit for interconnecting subscribers lines, a ringing relay for said'link circuit operable upon the connection of the link with a called line to apply ringing current thereto, a selflocking relay thrc ugh the windings of which current is supplied to a substation through the calling end of the link circuit operable upon energiza tion to disable said ringing'relay, and a locking circuit for said self locking relay maintained closed only during the connection of the link circuit with a called line.

CHESTER C. ALLE R. OLE BEKKEDAHL.

Washington, D. G. 

